Summary While upbound in the Amherstburg Channel the bottom plating and turn of the bilge on the port side of the VULCAN contacted an underwater obstruction after the vessel left the channel. Damage was caused to the vessel's ballast tanks Nos. 1 and 2. No one was injured nor was pollution caused. Ce rapport est galement disponible en franais. Other Factual Information Early morning on 06 November 1996 the VULCAN was under the conduct of a U.S. pilot, proceeding upbound in the Amherstburg Channel. The pilot made use of both radars which were in operation. Also on the bridge were the master, officer of the watch(OOW), helmsman and occasionally the watchman. The vessel was on the western, deeper side of the channel which is designated by VTS Traffic for upbound vessels with deeper draughts. At approximately 0230[1] the vessel was near the upper end of Bois Blanc Island. The weather was clear with good visibility and the water level was 0.77 metres above chart datum. The current in the area was estimated to be between 1.5 to 2 knots. According to the U.S. Coast Pilot No.6 and Canadian Sailing Directions, the strength of the current is between 0.8 and 1.2 knots. At about 0230, without prior notification of the intention to do so, a change-over from heavy fuel to diesel fuel was begun by the engine-room crew. The engine revolutions per minute (RPM) decreased from 110 to an unknown value (with a corresponding decrease in the vessel's speed) for an undetermined period of time. While passing light 'D69' and steering a course of approximately 003(T) degrees, the Global Positioning System (GPS) indicated a speed of 5.5 - 5.6 knots over the ground. The pilot decided to bring the vessel further towards the western side of the channel. He communicated his reason for doing so to the master and the OOW; he believed there was a stronger than normal current beyond light 'D71'. The master left the determination of 'how far' to bring the vessel to port, up to the pilot and did not challenge the pilot's decision. At the request of the pilot, the master called the engine room for more RPM. At light 'D71', the vessel had to make an alteration of course to port of 12.5 degrees; here the alignment of the channel changes from 350 to 342.5 degrees (T). In this area the Limekiln Crossing range lights are an aid to navigation which indicate, at light 'D69', the centre of the western half of the upbound channel. Neither the master nor OOW noted the significance of the Limekiln range lights at the time. At approximately 0240, the master went to the washroom at the back of the wheelhouse, while the port course alteration was taking place. While passing light 'D69' to port, the vessel was described as being several metres off the light and it was noted that the vessel appeared to be getting closer to the shore. The pilot asked for more engine RPM but cancelled this request immediately after the vessel was felt to strike on her port side. The striking was described as a 'slam'. At the time of the occurrence there was no other traffic in the area. The pilot did not appear to be concerned and indicated to the master that there wasn't any problem. Neither the master nor the OOW reported the occurrence to Vessel Traffic Services, Sarnia. At 0330 the pilot notified Vessel Traffic Services Sarnia that the VULCAN had developed a list to port and would have to go to anchor at Ojibway anchorage near Windsor, Ontario. The pilot also indicated that the vessel may have struck bottom. At 0635 VTC Sarnia was advised that the vessel was holed in ballast tanks Nos. 1 and 2 and had taken on about 700 tons of water. On arrival in Detroit, Michigan, the U.S. Coast Guard detained the vessel until an underwater survey for damage and seaworthiness had been completed and a repair proposal submitted. A change of fuel type when under way normally incurs a reduction in RPM. Except for this normal phenomenon, there was no mechanical difficulty or machinery problem noted at the time of the occurrence. Vessel Traffic Services had not issued a 'Notice to Shipping' concerning higher than normal currents in the area of the occurrence. The current was reported as being normal. Other vessels, more deeply laden than the VULCAN, navigated through this area without incident both before and after the occurrence. None of these vessels reported unusually strong currents or other difficulty. Previous to this assignment the pilot had taken two days off. After eight hours of restful sleep, he boarded the vessel at 0850 on 05 November at the Port Colborne anchorage. The master had made several trips into the Great Lakes in previous years, but in a lesser capacity than master. Following the pilot's report of the possibility of an underwater obstruction in the channel, two sounding surveys and bottom profile tests of the occurrence area were conducted by the Canadian Coast Guard, Amherstburg. No anomalous depth or obstruction was found in the channel nor, outside of the channel to within 12 to 24m of the shore. The distance from the western edge of the channel to the shore varies from 24 to 30 m. The VULCAN had 30 m of manoeuvring room on each side when in the centre of the deep portion of the channel. The GPS unit was examined and tested and showed the correct co-ordinates for latitude and longitude and its other functions were working correctly.